Effects of different loads on the surface of silver metal oxide contacts for general-purpose relays

Silver metal oxides have become very popular as contact materials in electromechanical switching devices due to their high resistance to erosion and contact welding. Initially, these materials were developed for contactors and circuit breakers. Investigations on silver metal oxide contacts for general-purpose relays were conducted in order to gain an insight into the effects and failure mechanism of such contacts under specific loads, such as resistive and inrush current loads. It will be shown that contact failures may be influenced by very thin silver layers on the surface of silver metal oxide materials and the behavior of these layers at thermal stress. The silver layers are a result of the mechanical treatment in the production of rivets and the following riveting process. The results support the development of new silver metal oxide materials for general-purpose relay applications.